This application relates to an improved release tool for a spring brake actuator that cages the power spring of the brake actuator without axial movement outwardly of the actuator housing.
Spring brake actuators are utilized on modern heavy vehicles to actuate a brake when the vehicle is parked, or when a portion of the vehicle brake system fails. In either situation, a powerful spring expands to move a mechanical rod that actuates the brake actuator. This actuation will sometimes occur while the vehicle is on the road. An operator of the vehicle will then need to cage the spring such that the vehicle may be moved. Servicing of a spring brake actuator and, in particular, servicing of the parking side (where the power spring is located), is not recommended. Even so, in the event that one does attempt to open the parking side, the spring must be caged by a mechanical element prior to any such opening. The power spring is also typically caged when the actuator is removed, installed or when the vehicle is towed.
Thus, release tools have typically been provided in the parking side of a spring brake actuator. The release tools have typically been a bolt that is received within a piston that holds the power spring. When the bolt is turned it pulls the power spring piston toward an outer end of the housing, holding or "caging" the spring. The bolt has typically moved axially outwardly of the housing as it is turned. Thus, in prior art spring brake actuators, the release bolt typically extends axially outwardly from an outer end of the brake actuator housing when the power spring is fully caged.
While this type of release bolt has proven successful, in many applications, there may not be sufficient axial room for the release bolt to extend axially from the brake actuator. Thus, there are desirable benefits to providing a release bolt that does not extend axially away from the actuator when the power spring is caged. The prior art has not successfully provided an arrangement to achieve the goal of allowing reliable caging of the power spring, while at the same time not requiring additional axial clearance at the outer end of the spring brake actuator chamber.
In one proposed prior art spring brake actuator, a well or space received the release bolt and extended far into the housing. In fact, the release bolt extended axially inwardly beyond portions of the power spring. Such an arrangement provides some room for outward movement of the release bolt during caging. However, the proposed prior art system does not indicate that the brake would be fully caged when the release bolt head is aligned with the outer end of the housing. Thus, the bolt may need to extend outwardly from the housing. Moreover, in the proposed configuration, it would appear that a long socket wrench would be required to turn the bolt, and would itself require additional axial space. As such, this proposed prior art spring brake does not achieve the goals of the present invention.